Hey jacques,
Have you tried to at least start backing up the drive ?
The 29 hours may be an estimate, that drops very quickly to a more reasonable number once you start the process.

The reason I say that is I just swapped out the main drive in my macpro.
I used Carbon Copy cloner ( which works great BTW, http://www.macupdate.com/app/mac/7032/carbon-copy-cloner ).

My original drive was a 250 Gig and the new one was 500 Gig. There was about 200 Gigs on the old drive to be transferred.
At the start of the process it told me it was going to take 18 hours ( !), but after about 30 minutes that dropped to 8 hours, and in the end it took about 5.

Hopefully this helps.

- Jay

MacPro 5,1/12 core@3.46GHz -- OS X 10.15.7 -- ATI 7970 -- 32 Gig RAM -- Crucial 500GB OS SSD -- Samsung EVO 1TB Audio/Sample SSD -- BIAB 2023 -- Logic Pro X -- Cubase Elements 11 -- Too many plugins